grazing incidence x-ray fluorescence analysis and …chateign/formation/course/xrr...grazing...
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Grazing incidence X-Ray Fluorescence Analysis
and X-Ray Reflectivity
Giancarlo Pepponi Fondazione Bruno Kessler MNF – Micro Nano Facility
MAUD school 2016
Caen, France
1 GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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acknowledgements
Fabio Brigidi - Elettra, Trieste, Italy
Christina Streli – Technische Universität Wien – Atominstitut,
Vienna, Austria
Dieter Ingerle – Technische Universität Wien – Atominstitut,
Vienna Austria
Florian Meirer – Universiteit Utrecht, Netherlands
Luca Lutterotti – Università degli studi di Trento, Trento, Italy
Mauro Bortolotti – Università degli studi di Trento, Trento, Italy
Daniel Chateigner – CRISMAT, Ensicaen, IUT, Caen, France
Magalì Morales – CIMAP, Ensicaen, ESPE-Caen, Caen, France
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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XRF configurations
XRF
bulk analysis
micro-XRF
2D - 3D micrometer spot
grazing incidence
TXRF
GI-XRF
XSW
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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XRF GIXRF
Why?
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XRF GIXRF
A. H. Compton, The total Reflection of X-Rays, Phil. Mag., 45, 1121; 1923
Pictures from the Nobel Lecture, December 12, 1927
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Snell’s law – optical region
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Snell’s law – x-ray region
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Snell’s law – x-ray region
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Index of refraction – decrement - delta
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Critical angle for total reflection
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Snell’s law – absorption
Au sheet
Calculated for E = 17500eV
I0
I(x)
0 50 100 150 200 250 300 350 400 450
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Inte
nsity [a
rbitra
ry u
nits]
distance [µm]
Beer-Lambert‘s Law:
)exp()( 0 µxIxI
Linear absorption coefficient:
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Snell’s law – x-ray region – with absorption
medium 1 is vacuum Total external reflection
heterogeneous wave
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Beta – absorption
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Atomic form factor
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photoelectric absorption
corrections for photoabsorption (Kramers-Kronig dispersion) relativistic effects, nuclear scattering
‘anomalous’ energy dependent terms
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Atomic form factor (forward direction)
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
forward scattering factors (x = theta = q = 0)
f1 and f2 are directly related to the index of refraction (reflection, refraction, XRR)
photoabsorption
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Fresnel – reflected intensity
Propagating electromagnetic field
Photon Energy
Energy of the electromagnetic field, number of photons
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Fresnel – 2 media
Electric vector perpendicular to the plane of incidence (s, TE, polarisation ) In German senkrecht = perpendicular
Approximations (ignore quadratic terms):
Same formalism as for XRR X-Ray Reflectivity
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Reflectivity
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Reflectivity
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Reflectivity
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Fresnel – x-ray region – exact
Complex dielectric constant
B.L. Henke, Phys. Rev. A, 6, 1, (1972) M.-R. Lefévère, M. Montel, Opt. Acta 20, 97 (1973)
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Fresnel – approximated vs exact - angle of refraction
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Fresnel – approximated vs exact - transmission
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GIXRF - intensity calculation – 1 interface – thin layer
P. Kregsamer, (1991), Spectrochimica Acta Part B, 46(10), 1332–1340. (1991)
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‘diluted’ dopant profile
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
G. Pepponi et al. / Spectrochimica Acta Part B 59 (2004) 1243–1249
optical properties of the substrate are used
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Multiple layers
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L. Parratt, Physical Review, 95(2), 359–369, 1954
X-Ray Reflectivity (but GIXRF also “given”)
In the optical range: F. Abeles, Le Journal de Physique et le Radium, "La théorie générale des couches minces", 11, 307–310 (1950) Recursive transfer matrix method, used also for XRR
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Multiple layers
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‘non ‘diluted’ doping profiles
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
optical properties calculated for each layer each layer a different material
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‘non diluted’ doping profiles
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Total reflection, OK, but practically?
The interference of incident and reflected beam causes a standing wave field above the reflectors surface.
Intensity distribution as a function of incident angle and depth
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Total reflection, OK, but practically?
TXRF – analysis of surface contamination analysis of materials deposited on flat reflecting surface GIXRF – get “positional-structural” (as well as chemical) information through the angular dependence of fluorescence in the grazing incidence region: above-below surface film-like, particle-like particle size layered samples XSW – standing wave field created by interference of incident and Bragg reflected field but also the study of crystalline like “super-structures” (e.g. Langmuir-Blodgett films)
EDX-
detector
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Quantitative analysis
Empirical methods
First principles / fundamental parameters - deterministic - Monte Carlo
PROS No physical model needed CONS Need of SPECIFIC standard samples One calibration per experimental condition APPLICATION Good for monitoring very similar samples
PROS NON SPECIFIC standard samples used to evaluate model parameters One calibration per experimental condition CONS Need a physical model to simulate results APPLICATION Good if samples keep changing
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Quantitative analysis
PROS NON SPECIFIC standard samples used to evaluate model parameters One calibration per experimental condition CONS Need a physical model to simulate results APPLICATION Good if samples keep changing
Describe/model - source - detector (efficiency) - sample Interactions: - scattering - photoelectric absorption - fluorescence/auger Fundamental Parameters
First principles / fundamental parameters - deterministic - Monte Carlo
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Quantitative analysis
First principles / fundamental parameters - deterministic - Monte Carlo
PROS NON SPECIFIC standard samples used to evaluate model parameters One calibration per experimental condition CONS Need a physical model to simulate results APPLICATION Good if samples keep changing
Peak intensity Extraction Intensity simulation/comparison/fitting
Spectrum (spectra) simulation/comparison/fitting
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Quantitative analysis
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Monochromatic
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Fundamental parameters
- Standard Atomic Weight: IUPAC recommended values - Elemental densities: J. H. Hubbell and S. M. Seltzer - Electron binding energies, Edge Jump, X-Ray lines, Transition probabilities, Fluorescence yield, Cascade effect: xraylib, T. Schoonjans et al. - Atomic energy level widths: J. L. Campbell, T. Papp - Fluorescence yield, Coster-Kronig probabilities: M. O. Krause - Atomic scattering factors (150eV-30000eV): B. L. Henke et al. - Atomic scattering factors (30000eV - 300000 eV): S. Brennan et al. - Phoelectric (shell-specific and total), elastic and inelastic scattering cross sections: H.Ebel et al.
https://data-minalab.fbk.eu/txrf/xraydata/
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Fundamental parameters
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Sample
Experimental Parameters
Elements
Materials
Layers
( Contamination/dopant Profile )
Nanoparticles
Experimental Set-up
(primary beam, detector)
Geometrical Configuration
Simulation
Experimental Data
Data Fittin
g
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Fundamental parameters
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Elements
Materials
Layers
( Contamination/dopant Profile )
Nanoparticles
In XRF: Cross sections are tabulated in cm^2/g For single elements
To define a material in XRF you must provide: Weight fractions and density
In XRD: you just need the phase parameters
Phases
Layers
( Contamination/dopant Profile )
Nanoparticles
SiO2 (native)
Si (bulk)
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Example : doped silicon surface
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Si (bulk)
SiO2 (native)
Arsenic concentration
cm at
om
s /
cm^3
20nm
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GIXRF quantitative analysis
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
0.1 deg simulated spetrum
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GIXRF quantitative analysis
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XRR
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
GIXRF vs XRR ?
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GIXRF - intensity calculation – 1 interface
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
sensitive to electron density and its changes: - material density - film thickness - optical constants - roughness
reveals elemental surface concentrations: - material composition - in depth elemental information
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GIXRF vs XRR
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GIXRF - ambiguity problem - As doping profile
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
0 5 10 150
2
4
6
8
10
12
14x 10
21
depth [nm]
co
nc
en
tra
tio
n [
ato
ms
/cm
3]
Depth distribution of Arsenic
fit result
SIMS GIXRF fit result looks very good, almost no difference between calculation and measurement
… but the result for the depth distribution is unrealistic -> GIXRF is ambiguous
courtesy of Dieter Ingerle
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GIXRF - ambiguity problem – Hf thin film
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
GIXRF can only determine surface mass concentration! Ambiguity thickness vs. density (XRR probably better)
GIXRF measurement data fitted to calculated values. This comparison shows the ambiguity of GIXRF concerning density and thickness. For the left side a layer-density of 6.7 g/m3 was used, while on the right 6.1 g/m3 was used
courtesy of Dieter Ingerle
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GIXRF - intensity calculation – 1 interface
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Si wafers implanted with 1E15 atoms/cm2 of Arsenic by beamline ion implantation with different implantation energies: • As1 – 0.5keV • As3 – 2keV • As4 – 3keV
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Roughness
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L. Nevot, P. Croce, Revue de physique appliquée, 15, 761 (1980)
P. Croce and L. Nevot, Rev. Phys. Appl. 11, 113 (1976)
interface layers with changing index of refraction - error function , linear
factors multiplying the Fresnel coefficient
All good for XRR but what about Fluorescence???
Can we model it as particles?
Multiply reflectivity and transmission by a damping factor
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Roughness
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Depth resolution – buried layers and interfaces
Definition of depth resolution:
- different at different depths
Sample 10nm In2O3 / 4nmAg / 10nm In2O3
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Depth resolution – junction depth
0 2 4 6 8 10 12 14 16
0.02
0.04
0.06
0.08
0.10norm
alis
ed A
s c
oncentr
ation [a.u
.]
depth [nm]
0 2 4 6 8 10 12 14 161E-3
0.01
0.1
no
rma
lise
d A
s c
on
ce
ntr
atio
n [
a.u
.]
depth [nm]
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
0
1
2
3
4
5
flu
ore
sce
nce in
ten
sity [
a.u
.]
angle [rad]0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
-0.006
-0.004
-0.002
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
diffe
ren
ce
am
on
g a
ng
ula
r
flu
ore
sce
nce
in
ten
sitie
s
angle [rad]
blu - black
blu - red
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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Fluorescence intensity cascade effect – secondary fluorescence
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Incident photon
Photoelectron
Fluorescence
photon
Incident photonIncident photon
PhotoelectronPhotoelectronPhotoelectron
Fluorescence
photon
Fluorescence
photon
Fluorescence
photon
Cascade photon
Secondary
fluorescence
photon
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Fluorescence intensity cascade effect – secondary fluorescence
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
GaAs solution deposited on silicon – Cascade – No Secondary Fluo
GaAs Wafer – No Cascade – No Secondary Fluo
GaAs Wafer – Cascade – Secondary Fluo
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GIXRF - secondary fluorescence
200 nm of ZnSe on Ge ZnK
GeKa1
SeKa1
GeK
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Geometric corrections
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Conway, John T. , Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 614.1 (2010): 17-27.
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Divergence
Divergence 0.5 mrad
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‘Strange’ angular fluorescence dependencies
????
And the happy end!
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GIXRF on plasma immersion doped samples
P2 As PIII (7s/ 50mTorr) Si as implanted P1 As PIII (7s/ 50mT0rr) Si RTA 1050°C
Very strange angle scan!!!
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GIXRF on plasma immersion doped samples
Confronting GI-XRF with theory reveals that it is hiding As containing surface particles/residues.
Characteristic shapes due the angular dependence of the fluorescence radiation for three different cases of atomic locations.
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GIXRF - particles
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GIXRF - particles
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Result: about 1/3 of the As is in particles
and 2/3 in the film-like doped layer
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Arsenolite crystals on the surface
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Following the trace of breadcrumbs we found that the particles are actually micro- and nano-crystals…
Si
As O
… crystals that are made of Arsenic and Oxygen …
… and melt in the electron beam. Total exposure time:
1h10min
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Extension of the wavefield - coherence
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Extension of the wavefield - coherence
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
courtesy of Dieter Ingerle
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Extension of the wavefield - coherence
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
courtesy of Dieter Ingerle
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Example Ge:Sn
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
SIMS measured profile
Beta curve
Si Ge Sn
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Example Al2O3 protective layers
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
Experimental Data
Simulation
Background
Al - Ka
Si - Ka
S - Ka
Ag - La University of Maryland
Prof. Ray Phaneuf
Amy Marquardt
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Example Al2O3 protective layers
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Example Al2O3 protective layers
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
𝐴𝑔4𝐶𝑢1.5𝑆1.5
Multiple Layers
Diffusion Profile
Nanoparticles
Nanoparticles Composition:
Sulphur Estimation
Nanoparticles Size:
Gaussian distrib. - xc: 30 nm ; σ 6 nm
(good agreement with AFM measurements)
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Grazing exit x-ray fluorescence
R. Becker, J. Golovchenko, J. Patel, PRL 50(3), 153–156
“the principle of microscopic reversibility predicts that the results of absorption- and emission-type experiments should be identical were they performed with the same wavelength radiation.”
GI-XRF
GE-XRF
Advantage: - higher lateral resolution Disadvantage: - reduced sensitivity
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Grazing exit
SSRL beamline 10-2 mesoprobe setup pinhole: spotsize 500µm2
Motivation: Check spatial homogeneity
S2R6C10
S2R6C11
Scan 180
200
190
Y [mm]
“the principle of microscopic reversibility predicts that the results of absorption- and emission-type experiments should be identical were they performed with the same wavelength radiation.” Becker et al.
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Grazing exit
Motivation: Check spatial homogeneity of annealing
increasing angle Motor position
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GIXRF/XRR software - JGIXA
Dieter Ingerle – ATI - TuWien
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
courtesy of Dieter Ingerle
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XRF/GIXRF/XRR software - GIMPY
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
• ED-XRF • GI-XRF • GE-XRF
• Spectrum Simulation
• XRR
SciPy library
Computation/Simulation
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The Software
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi
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THANKS FOR YOUR
ATTENTION
GIXRF and XRR– MAUD school 2016 – Giancarlo Pepponi